(SPOILER)Actually, I think I had to go in and do a combo to finish him off when he got weak, since now that I recall, poison stops doing damage when you reach 1 HP in this game.

And yes, mages do start to suck after a point, but I still find them useful if I wanted to say, grind magic crystals or something (Lightning Bolt + Rufus's Killer Thorn = 80 crystals a battle quite easily). But they definitely aren't anywhere near the level of power they were at in VP1.

But anyway, look at the power of 9,999 INT. (Might contain spoilers).